PCV bypass
 

Hey all. Tired of having performance and mileage sapped away by the good 'ol epa? Tired of having an oily dirty intake? Try this mod and increase performance and mileage. I have done this to both a HR350Z and now my 370Z and experienced over a mile per gallon increase. Performed wise is very little but if you're real in tune with your car you might notice it down low. The benefit comes from not sucking oil vapors and blow by vapors into your fresh combustion chamber and lowering your octane rating.
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Just a FYI this is illegal on a track since if the motor blows oil can come out the filters and onto the track. That's why people run a catch can or air oil separator still connected to the manifold since if the motor blows the oil is caught in the manifold and cylinders

Thanks for the info. I've never been to the track before. I have driven with this setup for a while though and never had a drop of leakage.

I ran with one of those, had a thin film of oil all over the engine bay... Wasn't worth it, but whatever works for you! :tiphat:

I wouldn't expect it but I'd like to see a test of your HP theory. Reason why is you've removed a slight pull of suction of the bottom of the pistons since the intake lines been broken. On bikes its been shown to add HP since the suction aids in piston travel. With your connection being broken you've lost that action. I'd vote a loss of power, not a gain. Unless however you suck so much oil into the cylinders you were losing power. I still say best of both worlds is a AOS. No oil, no lost suction.

I'll be getting to the dyno one of these days. I'll try and remember to do a pull with and without. But the way these pcv valves work they close off at higher rpms anyways so it really only effects lower range. But from a chemistry standpoint, you get a better combustion a higher octane rating and less knock.

OP
I've got a similar set up. I didn't remove the PCV 2 Ntake many lines though.
I let 'em pull at low RPM, like u said, they close @ high RPM. I dump the valve cover breathers on teh gr0und. No oil residue in my engine bay. :tup:

Oh that's a good idea to vent on the ground but if part of your system is still hooked up then your sucking unmeasured air and messing with your a/r ratio. Also if your still sucking from the pvc then your not getting the little benefit.

I know a subi is different but I used to vent to the ground also (very illegal for a track!!). Then I started getting faster in high G corners and was dumping all my oil out the valve cover breathers. My car was soaked in oil!!! That's why they have to run a catch and return system. But instead of hooking it up oem style to the mani where the motor will burn it up lowering HP, AFR, oil level, we hooked the return to the crank case breather so whatever got spit out went back in to a safer/better place. Not sure if its a Z problem but someone who can fuel starve in high G right handers would need to confirm yes or no.

OEM service manual PCV diagram
 

Let me modify page EC-509 of the '09 service manual to show you how I do it. Where the red x's are I placed K&N crank case breathers on the valve covers. This dumps to the ground/atmosphere. Where the red x's are on the intake (accordion tubes) I placed pipe plugs to seal the holes, no vacuum leaks. I do not remove the PCV valves or the hoses off of these to the intake manny. I simply do not want blow by gasses being dumped into my intake before the TBs during "full throttle" conditions. As LJ stated, this keeps the intake air CLEAN and COOLER, thus subsiding detonation.:tup:

So I just took all my catch can and stuff apart (had a leak). I've noticed my hoses on the front of the mani coming from the catch can now have oil in them. But that's impossible because my catch can doesn't allow this! So I'm assuming the oil is not coming from the catch can/PCV valves, but from the inside of the manifold since my Z1 post tubes still are hooked up normal to the valve covers?

I'm not doing a dump to atmos when I have a proper CC! But I'm not sure I feel comfortable blocking off the post tube port and the valve cover head. Its gotta be there for a reason.

I'm not sure exactly how catch cans are made but from what I've seen they are made like a baffle? With no real filter in them. Am I right? If so, then they're not doing what they claim to do because the oil and blow by are in the form of vapors, which will stay in the air until they land on something. So no matter how many baffles there are, some vapors will always get through.

Technically a catch can is literally just a can. Once you add baffle you've made a air/oil separator or AOS. Some people throw steel wool into a catch can but a real AOS has a baffle system. Here's a pic of what I use below. The inlets are angled so the air hits the sides and has to swirl around the sides collecting. If some is still air borne it has to make its way into the second chamber collecting on its sides. Then suspended in mid air is the return tube. Its impossible for oil to make it through everything. My subi, ram 1500 and Z have all had bone dry returns till the Z now. Since again I think its coming from the manifold under WOT and not the AOS.

Thanks for the CC picture post. Could you possibly be getting reverse suction from the fresh air tube's? I couldn't think of any other way that oil could build up in the manifold.

Idk, L33T thinks so it looks like.